Seam Felt for Papermaking and Manufacturing Method Thereof

ABSTRACT

A seam felt  10   c  for papermaking comprises wet paper web side batt layer  30   c  and seam region  12 . Fragments of a sheet-shaped nonwoven fabric  40   a , which is disposed at a region of the wet paper web side batt layer  30   c  adjacent to the seam region  12 , and which is crushed by means of needle punching, are dispersed within the widthwise range of the batt layer. At least a part of the fibers of the batt layer penetrates holes of the fragments of nonwoven fabric  40   a , and the fragments of nonwoven fabric  40   a  are melted by heat and adhere to fibers of the batt layer.

FIELD OF THE INVENTION

The present invention relates to a seam felt for papermaking and amanufacturing method thereof.

BACKGROUND ART

In recent years, mainstream papermaking apparatuses are the ones thatoperate at high speed and high pressure It is desirable for a press feltfor papermaking to have high permeability to liquid. Therefore, themainstream press felt is one wherein the fabric structure of the basicpart is made of monofilament, so that high permeability is achieved.

A conventional press fabric that can be seamed on a machine (for examplerefer to WO02/35000) comprises a batt and a strip made of flow-resistantmaterial, placed on or adjacent to the seam region of a papermaker'sfabric, so that the permeabilities of the seam region of the pressfabric to air and water are substantially identical to those of theother regions.

FIG. 6 is a machine direction sectional view of a conventional pressfabric 10′.

Press fabric 10′ comprises a base fabric 14′, which is woven frommonofilament yarns, and seam regions 12, which join the base fabric 14′into endless form on the machine.

The base fabric 14′ is a woven fabric comprising machine direction weftyarns 16′ and cross-machine direction warp yarns 22′. The machinedirection yarns 16′ form seaming loops 18′.

Said seaming loops 18′ are interdigitated to create a passage for apintle 20′. The seaming loops 18′ and the pintle 20′ are combined tojoin the base fabric 14′.

A strip 24′ is disposed over the seam region 12′, straddling it byamount in the range from 0.5-2.0 inches (1.27-5.08 cm) on its top side.The strip 24′ is a ribbon of woven fabric, nonwoven fabric or polymericfilm, and is punched into the base fabric 14′ by needling. A batt 26,made of staple fiber, is driven into the base fabric 14′ at least fromone side thereof by needling or other means.

Batt 26 is cleared away from the seaming loops 18′ on the bottom side ofthe base fabric 14 to form a gap 28′.

A slit 30′ is cut obliquely through the batt 26′ and strip 24′. Thestrip 24′ provides a press fabric 10′ wherein the permeabilities to airand water of the seam region 12′ are not inferior to those of otherregions.

DISCLOSURE OF THE INVENTION

In the above-mentioned press fabric with a slit thereon, it wasnecessary to use a strip having suitable weight for maintaining orimproving the bondability of the batt placed on the seam region, inorder to prevent depilation. Inevitably, it was difficult to equalizethe permeabilities to air and water, and the physical property of thefelt (compressibility, permeability, and fouling component accumulation)in the seam region with those of other regions.

In a press fabric, since the texture of the wet paper web adjacent tothe seam region is altered in the papermaking process, if permeabilityto air and water, and the physical properties of the felt differ betweenthe seam region and other regions, there is a danger that the quality ofa wet paper web will fail, or the wet paper web will be torn. Moreover,there is a problem that the durability and the quality of a seam feltare spoiled.

Thus, the object of the present invention is to provide a seam felt forpapermaking and a manufacturing method thereof, wherein thedepilation-resistant property of a flap is improved, while the physicalproperties of the felt in the seam region are kept identical to those inother regions.

The present invention solves the above problems by providing a seam feltfor papermaking having a wet paper web side batt layer and a seamregion, characterized in that fragments of a sheet-shaped nonwovenfabric, fractured by needle punching, are dispersed in a region of saidwet paper web side batt layer adjacent said seam region within thedepthwise range of said batt layer, at least a part of the fibers ofsaid batt layer penetrates holes of said fragments of nonwoven fabric,and said fragments of nonwoven fabric melt by heat and adhere to fibersof said batt layer.

The invention also solves the above problems by providing amanufacturing method for a seam felt for papermaking, wherein a basefabric having seam loops is woven by a weaving machine, characterized inthat, when a batt layer is implanted into both sides of said base fabricto make a seam felt for papermaking in a needling process, asheet-shaped nonwoven fabric is disposed in a position adjacent saidseam loops, said sheet-shaped nonwoven fabric is fractured by needlepunching, fragments of nonwoven fabric are dispersed into said battlayer, a flap is formed by cutting said batt layer at the region of saidseam loops in a widthwise direction, and said fragments of nonwovenfabric are melted by heating.

According to the present invention, fragments of sheet-shaped nonwovenfabric are dispersed in a depthwise direction of a felt, so that thepermeabilities to air and water and the physical properties of the feltin the seam region approximate those of other regions.

Moreover, according to the present invention, depilation or falling offof batt fibers of a flap can be effectively prevented. As a result, thepresent invention can provide a seam felt for papermaking which has gooddurability and which can manufacture a wet paper web of high qualitywith less danger of tearing in the papermaking process.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a machine direction sectional view of a seam felt forpapermaking before the needle punching process.

FIG. 2 is a machine direction sectional view of a seam felt forpapermaking after the needle punching process, fragments of nonwovenfabric being enlarged.

FIG. 3 is an enlarged perspective view showing the forms of fragments ofnonwoven fabric and batt fiber after the needle punching process.

FIG. 4 is a machine direction sectional view of a seam felt forpapermaking wherein a slit is formed after the needle punching process,fragments of nonwoven fabric being enlarged.

FIG. 5 is a machine direction sectional view of a seam felt forpapermaking after a heating process, fragments of nonwoven fabric beingenlarged.

FIG. 6 is a machine direction sectional view of a conventional pressfabric.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1 is a machine direction sectional view of a seam felt forpapermaking before the needle punching process.

In addition, “machine direction (MD)” is a longitudinal (length)direction toward which a seam felt is conveyed in a papermaking machine;and “cross-machine direction” (CMD) is a latitudinal (width) directioncrossing the above direction toward which a seam felt is moved in apapermaking machine.

At first, a weaving process of a base fabric 20 is explained.

A base fabric 20 is produced by weaving longitudinal yarns (machinedirection yarns) 22 and latitudinal yarns (cross-machine directionyarns) 24 with ends on a weaving machine.

In a seam region 12 of said base fabric 20, so-called seam loops 23, 23are formed on said longitudinal yarns 22, 22.

Said seam loops 23, 23 are so arranged as to line up with one another incross-machine direction. A stick core wire (a pintle wire) 26 isinterposed between said seam loops 23, 23 to make said base fabric 20endless.

In the needling process, which occurs next, a batt layer 30, comprisingbatt fiber 32, is intertwined by needle punching with both sides of saidbase fabric 20 to make said seam felt 10 into a papermaker's felt.

In above needle punching process, a single or multi layer sheet-shapednonwoven fabric 40 is placed in or on the surface of the batt layer 30at the seam region 12. Specifically, it is preferable that thesheet-shaped nonwoven fabric 40 be placed on the side of the seam loops23, 23 toward the side that contacts a wet paper web, in the way that itcovers the overall width of the seam felt 10 along the cross-machinedirection. Preferably, the length of the sheet-shaped nonwoven fabric 40in the machine direction is in the range from 1 to 20 cm.

In a seam felt 10 a (refer to FIG. 2) produced by a needle punchingprocess, the sheet-shaped nonwoven fabric 40 is crushed in the vicinityof the seam region 12 to form fragments of nonwoven fabric 40 a. As aresult, fragments of nonwoven fabric 40 a are dispersed about the seamregion 12 through almost the entire depth of the batt layer 30 a. Alongwith dispersion, the batt fiber 32 penetrates holes 41 a in thefragments of nonwoven fabric 40 a, as shown in FIG. 3.

Next, as shown in FIG. 4, the core wire 26, which was interposed in theseam loops 23, 23 of the seam felt 10 b produced by needle punchingprocess, is pulled out. Then, in a region above the location of the corewire 26, a slit 11 is formed in a batt layer 30 b in the cross-machinedirection of the seam felt 10 b, the slit extending obliquely toward thebase fabric 20.

The reason why the slit 11 is slanted relative to the machine directionby cutting the batt layer 30 b diagonally is that it is less likely thatmarks at the seam region will be transferred to a wet paper web than inthe case where the batt layer is cut vertically in the cross-machinedirection. On the other hand, a cut 11′ below the location of the corewire can be vertical.

As shown in FIG. 4, a triangular section having slit 11 as itshypotenuse serves as a flap f. In this case, the direction of travel ofthe seam felt 10 b on a papermaking machine is from the right to theleft in FIG. 4.

In a hot pressing process occurring after above-described processes, thecore wire 26 is put through the seam loops 23, 23 once again, and theendless seam felt 10 b is laid over between a pair of rolls, which arenot illustrated. By means of a heat source (not shown) arranged betweensaid pair of rolls and a press roll, the seam felt 10 b is hot pressed.The above hot pressing operation is optional, and sometimes only heatingis applied.

As shown in FIG. 5, fragments of nonwoven fabric 40 a are melted by ahot pressing process, and the melted fragments of nonwoven fabric 40 cadhere to the points where the longitudinal yarns 22, the latitudinalyarns 24, and the batt fiber 32 contact one another, and to the regionswhere the batt fibers 32 contact one another.

Thus, without damaging permeability to air and water, and the physicalproperties of the seam region 12 (compressibility, permeability, andfouling component accumulation), the present invention effectivelyprevents depilation and falling off of batt fibers 32 of flap f.

In addition, by pulling out the core wire 26 from the seam loops 23, 23of the endless seam felt 10 c after the hot pressing process, the seamfelt 10 c can be separated into a form with ends. Thus, the seam felt 10c can be packaged and shipped in rolled condition.

Therefore, when applying in a papermaking machine, after one end of aseam felt 10 c having ends is put into the machine, and the seam felt 10c surrounds rolls of the papermaking machine, by engaging the seam loops23 at one end with the seam loops 23 at the other end, interposing thecore wire 26, and connecting seam felt 10 c at the seam region 12, theseam felt 10 c can be rejoined into an endless form on the machine.

Preferably, the sheet-shaped nonwoven fabric 40 of the present inventionis a sheet-shaped fiber assembly made of spunbond, melt blown orspunlace filament or staple fiber.

For good dispersion of the sheet-shaped nonwoven fabric 40 in the needlepunching process, it is preferable that the sheet-shaped nonwoven fabric40 be relatively lightweight. It is therefore preferable to put in placea plurality of sheet-shaped nonwoven fabrics, the basis weight or arealweight of each of which is about 12 g/m².

The preferable materials for the sheet-shaped nonwoven fabric 40 arecopolymerized nylon, the fusing point of which is in the range from 120to 180 degrees Celsius, and copolymerized polyester or polyolefin, i.e.,materials that have a lower fusing point than the materials of the basefabric 20 and the batt layer 30, such as nylon, polyester, aromaticnylon, polyester or polyether-ester.

INDUSTRIAL APPLICABILITY

The present invention is able to make the permeabilities to air andwater, and the physical properties of the felt in the seam regionapproximate those of other regions. Moreover, the present invention canprovide a seam felt for papermaking which has good durability and whichcan manufacture a wet paper web of high quality with less danger oftearing in the papermaking process.

1. A seam felt for papermaking having a wet paper web side batt layerand a seam region, characterized in that: fragments of a sheet-shapednonwoven fabric fractured by needle punching are dispersed in a regionof said wet paper web side batt layer adjacent to said seam regionwithin the depthwise range of said batt layer; at least a part of fibersof said batt layer penetrates holes of said fragments of nonwovenfabric; and said fragments of nonwoven fabric melt by heat and adhere tofibers of said batt layer.
 2. A method of manufacturing a seam felt forpapermaking, wherein a base fabric having a seam loop is woven by aweaving machine, characterized in that, when a batt layer is implantedinto both sides of said base fabric to make a paper making seam felt ina needling process: a sheet-shaped nonwoven fabric is disposed at aposition adjacent said seam loop; said sheet-shaped nonwoven fabric isfractured by needle punching, and fragments of nonwoven fabric aredispersed into said batt layer; a flap is formed by cutting said battlayer at the region of said seam loop in a widthwise direction; and andsaid fragments of nonwoven fabric are melted by heating.
 3. A method ofmanufacturing a seam felt for papermaking according to claim 2, whereinsaid sheet-shaped nonwoven fabric is made of a material the fusing pointof which is in the range from 120-180 degrees Celsius.